/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */
package net.sf.freecol.common.networking;

import net.sf.freecol.common.model.Colony;
import net.sf.freecol.common.model.Game;
import net.sf.freecol.common.model.Player;
import net.sf.freecol.common.model.Unit;
import net.sf.freecol.common.model.WorkLocation;
import net.sf.freecol.server.FreeColServer;
import net.sf.freecol.server.model.ServerPlayer;

import org.w3c.dom.Element;


/**
 * The message sent to handle changes in work location.
 */
public class WorkMessage extends DOMMessage
{

    /** The identifier of the unit. */
    private final String unitId;

    /** The identifier of the work location.  */
    private final String workLocationId;


    /**
     * Create a new <code>WorkMessage</code> for the supplied unit and
     * work location.
     *
     * @param unit The <code>Unit</code> to change the work location of.
     * @param workLocation The <code>WorkLocation</code> to change to.
     */
    public WorkMessage( Unit unit, WorkLocation workLocation )
    {
        super( getXMLElementTagName( ) );

        this.unitId = unit.getId( );
        this.workLocationId = workLocation.getId( );
    }

    /**
     * Create a new <code>WorkMessage</code> from a supplied element.
     *
     * @param game The <code>Game</code> this message belongs to.
     * @param element The <code>Element</code> to use to create the message.
     */
    public WorkMessage( Game game, Element element )
    {
        super( getXMLElementTagName( ) );

        this.unitId = element.getAttribute( "unit" );
        this.workLocationId = element.getAttribute( "workLocation" );
    }


    /**
     * Handle a "work"-message.
     *
     * @param server The <code>FreeColServer</code> handling the message.
     * @param player The <code>Player</code> the message applies to.
     * @param connection The <code>Connection</code> message received on.
     * @return An update encapsulating the work location change or an
     *     error <code>Element</code> on failure.
     */
    public Element handle( FreeColServer server, Player player,
                           Connection connection )
    {
        final ServerPlayer serverPlayer = server.getPlayer( connection );
        final Game game = server.getGame( );

        Unit unit;
        try
        {
            unit = player.getOurFreeColGameObject( unitId, Unit.class );
        }
        catch ( Exception e )
        {
            return DOMMessage.clientError( e.getMessage( ) );
        }

        if ( ! unit.hasTile( ) )
        {
            return DOMMessage.clientError( "Unit is not on the map: "
                                                   + unitId );
        }

        Colony colony = unit.getTile( ).getColony( );
        if ( colony == null )
        {
            return DOMMessage.clientError( "Unit is not at a colony: "
                                                   + unitId );
        }

        WorkLocation workLocation
                = game.getFreeColGameObject( workLocationId, WorkLocation.class );
        if ( workLocation == null )
        {
            return DOMMessage.clientError( "Not a work location: "
                                                   + workLocationId );
        }
        else if ( workLocation.getColony( ) != colony )
        {
            return DOMMessage.clientError( "Work location is not in the colony"
                                                   + " where the unit is: " + workLocationId );
        }
        else if ( ! workLocation.canAdd( unit ) )
        {
            return DOMMessage.clientError( "Can not add " + unit
                                                   + " to " + workLocation
                                                   + ": " + workLocation.getNoAddReason( unit ) );
        }

        // Work.
        return server.getInGameController( )
                .work( serverPlayer, unit, workLocation );
    }

    /**
     * Convert this WorkMessage to XML.
     *
     * @return The XML representation of this message.
     */
    @Override
    public Element toXMLElement( )
    {
        return createMessage( getXMLElementTagName( ),
                              "unit", unitId,
                              "workLocation", workLocationId );
    }

    /**
     * The tag name of the root element representing this object.
     *
     * @return "work".
     */
    public static String getXMLElementTagName( )
    {
        return "work";
    }
}
